This invention relates generally to the quality of helically scanned magnetic tapes, such as video tapes or digital audio tapes and, more particularly, to the location of signal losses for purposes of analysis.
Frequently, video information is recorded on magnetic tape for replay at a later time. The quality of such a tape and the picture obtained by playing it are affected by momentary losses of the recorded signal which are usually referred to as "dropouts." One way of determining the quality of a tape has been to count the number of dropouts during one or more sampling periods as disclosed, for example, by Wong et al. in U.S. Pat. No. 3,662,158. Such information is useful in grading recorded tapes but not in efforts to identify the causes of signal losses and improve recordings by reducing the number of dropouts. Valuable information as to the reasons for losses of signal has been obtained by searching for and locating individual dropouts in the field of a microscope. First, the film must be stained with a dispersion of fine iron particles. This technique is not only laborious and time-consuming but also inconclusive since only a fraction of counted dropouts can be located for analysis.